1. Field of the Invention
This invention relates to a treadmill exercise machine, and more specifically, to a treadmill exercise machine which automatically compensates for a change in the user's pace by using optical sensing to establish the user's position and increasing or decreasing the speed of the treadmill, accordingly.
2. Background of the Related Art
Treadmill exercise machines are known in which a user walks or jogs upon an endless belt or treadmill in order to exercise his muscles and/or to provide an aerobic workout. Typical treadmill exercise machines fall into two categories, powered and unpowered. Typical unpowered treadmill machines may have an endless belt or treadmill disposed within a floor mounted chassis. A handle or railing may extend up from the chassis for the user to hold onto and push against while exercising. The force of the users legs on the treadmill cause it to move in an endless loop along rollers, pulleys or the like. An adjustable damping device is typically provided to provide resistance to the forward running or walking motion exerted by the user.
Typical powered treadmill exercises machines are constructed much in the same way as described above, except that they include a motor for powering the endless belt treadmill at one or more desired speeds. A handle or other grip may be provided for balance, but is not required for operation of the machine. The speed of the treadmill is determined by the rotational speed of the motor which drives the treadmill. The motor speed may be preset or it may be adjustable, depending upon the intensity of the workout desired.
In some cases it is desirable for a user to run at alternating speeds, such as for interval training, wherein the user alternates exercise intensity between two or more levels. Alternatively, a user may vary his speed during a workout due to simple fatigue over time. In those cases, however, a drawback of conventional powered treadmill exercise machines is that they run at a constant speed regardless of the speed of the user.